Purpose: Whole eye transplantation (WET) represents a pioneering frontier in transplant medicine, offering a potential cure for irreversible blindness. The success of WET hinges on the seamless integration of the transplanted eye with the host’s visual pathways. This study employs Visual Evoked Potentials (VEPs) and Electroretinography (ERG) post-operatively to evaluate graft function and visual pathway integration following the first human WET. VEPs assess the electrical responses of the visual system to stimuli, while ERG evaluates retinal cell activity, together providing insights into the functional restoration post-transplant, thereby paving the way for potential advancements in transplant medicine and visual rehabilitation.
Methods: Post-operative assessments after the first successful WET on a 46 year-old male were conducted using Visual Evoked Potentials (VEPs) and Electroretinography (ERG). VEPs utilized ISCEV standard and custom protocols at 3 and 30 cds/m^2 stimulus intensity respectively, both at 0.99 Hz. ERG employed a custom protocol at 30 cds/m^2 intensity and 28.3 Hz. Electrodes were positioned per the International 10-20 system for VEP. Analyzing VEP and ERG waveforms for latency and amplitude provided insight into the functional status of visual pathways, retinal function, and potential early signs of post-operative complications.
Results: Initial testing on postoperative day 9 demonstrated a non-measurable signal on ERG recording. However, progression of results from POD45, 67, 81, and 110 demonstrated recognizable waveforms with amplitudes of 4.5μv, 4.8μv, 5.9μv, and 5.5μv, respectively. Implicit time, a measure of conductive speed across the retina, demonstrated a steady decline with a result of 31.6ms on POD45 to 29.9ms on POD 110. VEP results were consistent with a distinguishable waveform, thought blunted, in the transplanted eye. On POD80, Pmax-Nmin of the transplanted eye was 5.2μv and 7.4μv in the 30cd and 3cd protocols respectively. Time to P2, a measure of latency between stimulus and measurable response, was 131.8ms and 119.2ms in the 30cd and 3 cd protocols, respectively, in the transplanted eye.
Conclusion: Post-operative assessments reveal promising functional integration post WET. Measurable VEP in the transplanted eye indicates successful optic nerve integration and transduction of signal to the optic cortex. Initial ERG showed diminished amplitude in the transplanted eye, hinting at reduced retinal responsiveness. However, a gradual increase in ERG amplitude over time suggests potential retinal recuperation or adaptation. These findings, particularly the progressive improvement in retinal responsiveness, underscore the success of the inaugural WET, illustrating the potential of this pioneering surgical intervention for vision restoration.